Today, radiation imaging systems such as computed tomography (CT) systems, single-photon emission computed tomography (SPECT) systems, digital projection systems, and/or line-scan systems, for example, are useful to provide information, or images, of interior aspects of an object under examination. The object is exposed to rays of radiation photons (e.g., x-ray photons, gamma ray photons, etc.) and radiation photons traversing the object are detected by a detector array positioned substantially diametrically opposite a radiation source relative to the object. A degree to which the radiation photons are attenuated by the object (e.g., absorbed, reflected, etc.) is measured to determine one or more properties of the object, or rather aspects of the object. For example, highly dense aspects of an object typically attenuate more radiation than less dense aspects, and thus an aspect having a higher density, such as a bone or metal, for example, may be apparent when surrounded by less dense aspects, such as muscle or clothing.
Radiation imaging systems are utilized in a variety of fields to image/examine aspects of an object not readily visible to the naked eye. For example, radiation imaging systems are used in security applications to identify potential threat items, including weapons and/or explosives, concealed within a suitcase or other object, for example.
Two of the more common types of radiation imaging systems used in security applications are CT systems and line-scan systems. Line-scan systems are configured to view the object from a limited number of view-angles (e.g., typically 1 view-angle) and generate projection images (e.g., 2D images) respectively representing a collapsed or flattened, 2D view of the object (e.g., where the densities of aspects of an object through a line in which radiation travels are integrated and represented as a single point on the 2D image). Such systems are particularly valuable for generating high resolution 2D images for display to security personnel responsible for identifying potential threat objects.
CT systems are configured to view an object from a greater number of view-angles than line-scan systems and to generate volumetric data representative of the object. In this way, a three-dimensional (3D) image of the object can be created and properties of respective aspects within the object, such as density information, z-effective information, shape characteristics, etc., can be determined. Using one or more of these properties, automated threat analysis can be performed to determine if the object is a potential threat item. Moreover, 2D projection images or 3D volumetric images can be obtained from CT systems that are representative of the object (e.g., although typically such images are of a lower resolution than the projection images generated by line-scan systems due to, among other things, differences in the resolution of CT detector arrays relative to detector arrays utilized in line-scan systems).
While automatic threat analysis algorithms have proven useful to identify potential threat items, it is sometimes desirable for a security screener to view images of the objects or aspects concealed therein. Accordingly, the resolution of images produced by a radiation imaging system is sometimes an important consideration when selecting whether to implement a line-scan system or a CT system in an environment.